text: Back when they first designed software, there was no confusion on dates. You could have the year read "50", "65", "80", or "95" with no problem. So, they coded the systems to only require those two digits and just added the 19 at the beginning. Well, when 1999 turned to 2000, those systems would think it was "1900". Any systems that relied on the date to keep things in order might break down by trying to run the "latest order" (that made on 12/31/1999) repeatedly, instead of the new orders. The Y2K hysteria that said planes would fall from the sky and nuclear weapons would launch themselves was just hyperbole. But it could have been a major problem in banking and trading software.